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Displaying Results 76 - 100 of 1489 on page 4 of 60
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Experimental observation of scaling laws for alternating current and direct current conductivity in polymer-carbon nanotube composite thin films
(2002)
COLEMAN, JONATHAN NESBIT; BLAU, WERNER; HUTZLER, STEFAN; DRURY, ANNA
Experimental observation of scaling laws for alternating current and direct current conductivity in polymer-carbon nanotube composite thin films
(2002)
COLEMAN, JONATHAN NESBIT; BLAU, WERNER; HUTZLER, STEFAN; DRURY, ANNA
Abstract:
Alternating current (ac) and direct current (dc) conductivities have been measured in polymer-nanotube composite thin films. This was carried out for a range of concentrations of multiwall nanotubes in two polymer hosts, poly(m-phenylenevinylene-co-2,5-dioctyloxyp-phenylenevinylene) (PmPV) and polyvinylalcohol (PVA). In all cases the dc conductivity σDC was ohmic in the voltage range studied. In general the ac conductivity displayed two distinct regions, a frequency independent region of magnitude σ0 at low frequency and a frequency dependent region at higher frequency. Both σDC and σ0 followed a percolation scaling law of the form σ∝(p−pc)t with pc=0.055% by mass and t=1.36. This extrapolates to a conductivity of 1×10−3 S/m for 100% nanotube content. Such a low value reflects the presence of a thick polymer coating, resulting in poor electrical connection between tubes. This leads to the suggestion that charge transport is controlled by fluctuation induced tunneling. In the high fr...
http://hdl.handle.net/2262/40261
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Mark
Improving the Mechanical Properties of Single-Walled Carbon Nanotube Sheets by Intercalation of Polymeric Adhesives
(2003)
COLEMAN, JONATHAN NESBIT; BLAU, WERNER
Improving the Mechanical Properties of Single-Walled Carbon Nanotube Sheets by Intercalation of Polymeric Adhesives
(2003)
COLEMAN, JONATHAN NESBIT; BLAU, WERNER
Abstract:
Organic polymers, such as poly(vinyl alcohol), poly(vinyl pyrrolidone), and poly(styrene), were intercalated into single-walled carbon nanotube sheets by soaking the sheets in polymer solutions. Even for short soak times, significant polymer intercalation into existing free volume was observed. Tensile tests on intercalated sheets showed that the Young’s modulus, strength, and toughness increased by factors of 3, 9, and 28, respectively, indicating that the intercalated polymer enhances load transmission between nanotubes.
http://hdl.handle.net/2262/40263
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Mark
Alternating and direct current characterization and photoinduced absorption studies of modified conjugated polymer thin films
(2004)
COLEMAN, JONATHAN NESBIT; BLAU, WERNER; DRURY, ANNA
Alternating and direct current characterization and photoinduced absorption studies of modified conjugated polymer thin films
(2004)
COLEMAN, JONATHAN NESBIT; BLAU, WERNER; DRURY, ANNA
Abstract:
Control of interchain separation enables the optical properties of polymer thin films to be altered. We present a thin film preparation technique that increases the free volume fraction in spin coated polymer thin films resulting in reduced interchain interaction. The polaron yield, measured using photoinduced absorption, was significantly reduced as a direct result of the increased interchain separation, leading to a higher value for the measured photoluminescence efficiency. Impedance spectroscopy showed an increase in permittivity, probably due to greater polarizability. Increases approaching one order of magnitude were observed for direct current hole conductivity and mobility values. Space charge limited conduction analysis suggests a narrowing of the highest occupied molecular orbital band tail on treatment resulting in reduced trapping. Single layer light emitting devices prepared using this technique were found to be significantly brighter and to have longer operating lifetimes
http://hdl.handle.net/2262/40264
Marked
Mark
Magnetic noise in MgO-based magnetic tunnel junction rings
(2010)
COEY, JOHN MICHAEL DAVID; FENG, JIA-FENG
Magnetic noise in MgO-based magnetic tunnel junction rings
(2010)
COEY, JOHN MICHAEL DAVID; FENG, JIA-FENG
Abstract:
Magnetization switching is investigated in ring-shaped MgO-based magnetic tunnel junctions with 168% tunneling magnetoresistance. Besides the forward and reverse onion states, two vortex states and several metastable states are observed for the ferromagnetic free layer. Electrical noise is used to characterize the low frequency magnetization dynamics; a stationary 1/ f noise spectrum is observed within each magnetic state but they are separated by noise peaks which show a 1/ f2 spectrum that is associated with slow random telegraph fluctuations. In the 1/ f region, the normalized magnetic noise parameter, mag, is shown to be consistent with the fluctuation-dissipation theorem.
http://hdl.handle.net/2262/40309
Marked
Mark
Inverted magnetoresistance in dual spin valve structures with a synthetic antiferromagnetic free layer
(2009)
COEY, JOHN MICHAEL DAVID; WU, HAN-CHUN; SHVETS, IGOR; FOWLEY, CIARAN
Inverted magnetoresistance in dual spin valve structures with a synthetic antiferromagnetic free layer
(2009)
COEY, JOHN MICHAEL DAVID; WU, HAN-CHUN; SHVETS, IGOR; FOWLEY, CIARAN
Abstract:
We report an oscillation of the giant magnetoresistance GMR ratio as a function of Ru layer thickness in the CoFe/Cu/ CoFe/Ru/CoFe SAF/Cu/CoFe/IrMn dual spin valve SV structure. A normal GMR with a positive sign is observed for the thickness of Ru providing a ferromagnetic interlayer exchange coupling IEC . The inverted GMR is observed for the thickness of Ru providing an antiferromagnetic IEC, which is consistent with IEC period across the Ru spacer as well as the electrical separation of the overall structure into two SVs connected in parallel.
http://hdl.handle.net/2262/40313
Marked
Mark
Antiferromagnetic interlayer exchange coupling between Fe3O4 layers across a nonmagnetic MgO dielectric layer
(2008)
ARORA, SUNIL KUMAR; WU, HAN-CHUN; SHVETS, IGOR
Antiferromagnetic interlayer exchange coupling between Fe3O4 layers across a nonmagnetic MgO dielectric layer
(2008)
ARORA, SUNIL KUMAR; WU, HAN-CHUN; SHVETS, IGOR
Abstract:
We have investigated the interlayer exchange coupling between the epitaxial spinel Fe3O4 layers across an insulating nonmagnetic MgO spacer. The epitaxial structure used for these investigations was Fe3O4 (10 nm)/MgO (0.8–3 nm)/Fe3O4 (10 nm)/NiO (15 nm) multilayers grown on MgO (100) substrates. We find that the two Fe3O4 layers are antiferromagnetic coupled through the MgO spacer when the MgO thickness is less than 1.5 nm. Furthermore, ab initio calculation of IEC for Fe/MgO/Fe indicates the importance of electrode states, in particular, partial oxidation of the ferromagnetic electrodes.
http://hdl.handle.net/2262/40318
Marked
Mark
Microtexture of magnetite thin films of (001) and (111) orientations on MgO substrates studied by electron-backscatter diffraction
(2008)
MURPHY, SHANE; ARORA, SUNIL KUMAR; SHVETS, IGOR
Microtexture of magnetite thin films of (001) and (111) orientations on MgO substrates studied by electron-backscatter diffraction
(2008)
MURPHY, SHANE; ARORA, SUNIL KUMAR; SHVETS, IGOR
Abstract:
The grain orientation of (001)- and (111)-oriented magnetite thin films grown on MgO substrates (film thickness of 100–400 nm) is analyzed by means of the electron-backscatter diffraction (EBSD) technique. The (001) surface after a short annealing in air (1 min, 250 °C) is characterized by the presence of tiny (diameter of 100–200 nm) misoriented islands, which have an influence on the antiferromagnetic coupling within the film. In the (111)-oriented films, such defects are found to be absent, and the films show a very homogeneous surface. The achieved spatial resolution enables further a cross-section analysis of a 400-nm-thick film with (001) orientation, even close to the interface MgO-magnetite.
http://hdl.handle.net/2262/40322
Marked
Mark
Progress towards spin-polarized scanning tunneling microscopy
(1992)
SHVETS, IGOR; COEY, JOHN MICHAEL DAVID
Progress towards spin-polarized scanning tunneling microscopy
(1992)
SHVETS, IGOR; COEY, JOHN MICHAEL DAVID
Abstract:
Solutions to the main problems in operating a spin‐polarized scanning tunneling microscope are discussed. Preliminary experimental results obtained in the course of implementing these solutions are reported. Atomic resolution on Si(111) and Si(100) is achieved with a scanning tunneling microscope (STM) using chromium and iron tips. Fabrication of antiferromagnetic tips of Cr, MnNi, and MnPt is described. A technique of preparation of clean (100) surfaces of Fe3O4 (magnetite) is given. Low‐energy electron diffraction patterns were obtained on Fe3O4 for the first time. The first STM experimental results obtained on magnetite in air and in ultrahigh vacuum are reported. Atomic resolution is obtained on Fe3O4 (100) with an ultrahigh vacuum scanning tunneling microscope using iron and tungsten tips. This is the first successful observation of atomic resolution on a ferromagnetic sample using a ferromagnetic tip.
http://hdl.handle.net/2262/40330
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Mark
Charge freezing and surface anisotropy on magnetite (100)
(1993)
SHVETS, IGOR; COEY, JOHN MICHAEL DAVID
Charge freezing and surface anisotropy on magnetite (100)
(1993)
SHVETS, IGOR; COEY, JOHN MICHAEL DAVID
Abstract:
Scanning tunneling microscope images of the (100) surface of slightly nonstoichiometric magnetite taken at room temperature show static arrays of pairs of Fe2+ ions with short‐range order, and a charge fluctuation time greater than 103 s. The surface appears to be a Wigner glass with electron pairs localized on adjacent ions as the basic unit. The explanation of Wigner localization at room temperature on the surface only is that the spin‐polarized minority‐spin band derived from dyz orbitals is stabilized and narrowed by the absence of an apicial oxygen from the B‐site octahedron. This leads to surface anisotropy where the Fe2+ spins are pinned normal to the {100} surfaces. Surface anisotropy is expected to outweigh bulk anisotropy in submicron particles.
http://hdl.handle.net/2262/40332
Marked
Mark
Influence of ferromagnetic substrate on the magnetoresistance of Cr film across a nonmagnetic insulating layer
(2003)
SHVETS, IGOR
Influence of ferromagnetic substrate on the magnetoresistance of Cr film across a nonmagnetic insulating layer
(2003)
SHVETS, IGOR
Abstract:
(5 nm) Cr/(x nm) MgO/Mn0.52Zn0.48Fe2O4 (MnZn spinel) substrate (1<x<7 nm), as well as (5 nm) Cr/(7 nm) MgO/glass substrate structures have been grown using molecular beam epitaxy. The influence of the MnZn spinel on the in-plane transport and magnetotransport properties of the Cr layer were studied. The existence of pinholes in the MgO layer was explored by evaluating resistance versus temperature, R(T), dependencies. A hump was observed on the R(T) curves for the MgO layer thickness (tMgO) less than 5 nm. This results from the electrical coupling between the Cr film and the MnZn spinel substrate through the pinholes in the MgO layer. A reversal of the magnetoresistance (MR) sign in Cr film was observed when tMgO is less than 7 nm. It is thought that the effect of the electrical coupling through the pinholes and the magnetostatic coupling are not the reasons for the observed negative MR. A model is proposed which suggests that the magnetic structure in the Cr film adjoining a ...
http://hdl.handle.net/2262/40377
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Mark
Method of increasing spatial resolution of the scanning near-field microwave microscopy
(2003)
SHVETS, IGOR; KANTOR, ROMAN
Method of increasing spatial resolution of the scanning near-field microwave microscopy
(2003)
SHVETS, IGOR; KANTOR, ROMAN
Abstract:
In this article we propose methods for the measurement of electric intensity of a microwave field above the surface of microwave circuits. Using miniaturized coaxial antennas and a special probe positioning system, we measure both the amplitude and the phase of the induced field above the device under test. We introduce a position/signal difference method to further increase the spatial resolution down to about 30 μm—about one order better than contemporary microwave scanning devices utilizing coaxial antennas. The effect is theoretically analyzed and experimentally verified. The probes are calibrated in a well-defined field standard to allow quantitative characterization of the measured field. Performance of our scanning system utilizing these methods is demonstrated using a PCB finger capacitor.
http://hdl.handle.net/2262/40380
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Scanning tunneling microscopy studies of the Fe3O4(001) surface using antiferromagnetic probes
(2003)
SHVETS, IGOR; MARIOTTO, GUIDO; MURPHY, SHANE
Scanning tunneling microscopy studies of the Fe3O4(001) surface using antiferromagnetic probes
(2003)
SHVETS, IGOR; MARIOTTO, GUIDO; MURPHY, SHANE
Abstract:
We have studied the (001) surface of a Fe3O4 single crystal using low-energy electron diffraction (LEED), Auger electron spectroscopy (AES) and scanning tunneling microscopy (STM). The STM measurements were performed using a novel tip of antiferromagnetic MnNi alloy. Atomically resolved STM images provide evidence of a surface terminated at the octahedral plane, with rows of Fe cations running along the 〈110〉 crystallographic axes. Two different kinds of Fe cations with a separation of 6 Å were imaged, while the periodicity between Fe cations of the same kind is about 12 Å. We propose an interpretation of the anomalous corrugation observed in terms of a spin polarized effect, resulting in magnetic contrast between Fe2+ and Fe3+ ions in octahedral coordination.
http://hdl.handle.net/2262/40381
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Mark
Enhancement of the magnetization saturation in magnetite (100) epitaxial films by thermo-chemical treatment
(2004)
SHVETS, IGOR
Enhancement of the magnetization saturation in magnetite (100) epitaxial films by thermo-chemical treatment
(2004)
SHVETS, IGOR
Abstract:
The effect of thermo-chemical treatment on the ease of saturation in a magnetic field of epitaxial magnetite (100) thin films grown on MgO (100) substrates was investigated. It was found that the films maintained a fully strained state with the MgO substrate during the treatment in air. No other iron oxide phase apart from the magnetite was observed in the treated film. Yet, remarkably the treated films showed a higher magnetization compared to that of original ones. A model involving a change in antiferromagnetic coupling at the antiphase boundaries during the treatment is proposed.
http://hdl.handle.net/2262/40383
Marked
Mark
Spin-polarized tunneling effects observed on the oxygen-terminated Fe3O4 (111) surface
(2004)
SHVETS, IGOR; MARIOTTO, GUIDO; MURPHY, SHANE
Spin-polarized tunneling effects observed on the oxygen-terminated Fe3O4 (111) surface
(2004)
SHVETS, IGOR; MARIOTTO, GUIDO; MURPHY, SHANE
Abstract:
Under oxidizing preparation conditions the magnetite (111) surface reconstructs to a highly ordered superlattice. This surface reconstruction represents an oxygen termination of the magnetite bulk. We employ spin-polarized (SP) scanning tunneling magnetization (STM) to study the spin-dependent tunneling between a magnetite (111) sample and an antiferromagnetic tip through a vacuum barrier. Atomic scale STM images show significant magnetic contrast corresponding to variations in the local surface states induced by oxygen vacancies. The local variations of the tunneling magnetoresistance around these vacancies correspond to 150%. By employing SP–STM measurements and first principles calculations we could conclude that an oxygen top layer considerably changes the SP properties of the magnetite surface.
http://hdl.handle.net/2262/40387
Marked
Mark
Study of in-plane magnetic anisotropy of ultrathin epitaxial Fe films grown on vicinal Mo(110) surface
(2004)
USOV, VICTOR; SHVETS, IGOR; MURPHY, SHANE
Study of in-plane magnetic anisotropy of ultrathin epitaxial Fe films grown on vicinal Mo(110) surface
(2004)
USOV, VICTOR; SHVETS, IGOR; MURPHY, SHANE
Abstract:
In situ surface magneto-optical Kerr effect was used in conjunction with scanning tunneling microscopy and low-energy electron diffraction to study the in-plane magnetic anisotropy of ultrathin Fe films on a vicinal Mo(110) substrate. A uniaxial anisotropy with the easy axis of magnetization along the [001] direction was found for this system down to nearly 2 monolayers coverage, contradicting the results of recent theoretical calculations. The easy axis of a step-induced anisotropy coincides with the surface step edges.
http://hdl.handle.net/2262/40388
Marked
Mark
Study of polarization-dependent energy coupling between near-field optical probe and mesoscopic metal structure
(2004)
SHVETS, IGOR
Study of polarization-dependent energy coupling between near-field optical probe and mesoscopic metal structure
(2004)
SHVETS, IGOR
Abstract:
We present an experimental study of the coupling of light from a probe of a scanning near-field optical microscope (SNOM) into a mesoscopic structure consisting of gold stripes with varying separations. We demonstrate that the coupling efficiency depends upon the polarization direction in the probe relative to the stripes as well as the separation between the lines. Two possible explanations for a contrast reversal effect in between s- and p-polarized light are given. One is based on the excitation of a quasi-transverse electric and magnetic mode in the mesoscopic transmission line. For this explanation we have made a prediction of the condition of the maximum coupling efficiency through the approach of impedance matching. The second explanation is based on surface plasmon excitation in the gold structure. The present results can also be of importance in the development of new concepts of probes for SNOM.
http://hdl.handle.net/2262/40389
Marked
Mark
Anisotropic transport behavior in ultrathin epitaxial Fe films on vicinal oxide substrates
(2005)
SHVETS, IGOR; MC EVOY, CIARAN
Anisotropic transport behavior in ultrathin epitaxial Fe films on vicinal oxide substrates
(2005)
SHVETS, IGOR; MC EVOY, CIARAN
Abstract:
Step-induced anisotropy of electron transport in ultrathin Fe film was investigated. The Fe films (2 and 10 nm) were deposited on vicinal MgO (100) substrate using molecular-beam epitaxy. It is found that the films with a thickness of 10 and 2 nm are continuous and discontinuous, respectively, which was determined from their resistivity values, the temperature dependency of the resistivity and the V–I curve. The enhanced magnetoresistance in the continuous and the discontinuous films was observed when the current flows parallel and perpendicular to the miscut direction, respectively. We suggest that the atomic steps in the continuous films nucleate additional domain walls acting as scattering centers and the extra scattering was introduced for the current perpendicular to the step edges. The mechanism of the influence of the atomic steps on the electron-transport properties is different in the continuous and discontinuous films. We further suggest that in the discontinuous films, th...
http://hdl.handle.net/2262/40391
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Mark
Exposition of semiconducting and ferromagnetic properties of pulsed-laser-deposited thin films of LaFe1-xNixO3 (x=0.3, 0.4, and 0.5)
(2005)
SHVETS, IGOR; ARORA, SUNIL KUMAR
Exposition of semiconducting and ferromagnetic properties of pulsed-laser-deposited thin films of LaFe1-xNixO3 (x=0.3, 0.4, and 0.5)
(2005)
SHVETS, IGOR; ARORA, SUNIL KUMAR
Abstract:
We have explored the possibility of ferromagnetic semiconducting property in the epitaxial thin films of LaFe1−xNixO3 x=0.3, 0.4, and 0.5 grown on 001 oriented LaAlO3 substrate. We observe that substitution of Ni in the series leads to the increase in conductivity of the samples with conduction being controlled by the disorder-induced localization of charge carriers. All these samples show ferromagnetic behavior at room temperature while their magnetization decreases with increase in Ni concentration in the composition. The results have been explained on the basis of the close interplay between the electrical and magnetic properties.
http://hdl.handle.net/2262/40393
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Mark
Influence of antiphase boundary density on the conduction noise properties of epitaxial magnetite thin films
(2005)
SHVETS, IGOR; ARORA, SUNIL KUMAR
Influence of antiphase boundary density on the conduction noise properties of epitaxial magnetite thin films
(2005)
SHVETS, IGOR; ARORA, SUNIL KUMAR
Abstract:
Low frequency conduction noise (1/f noise) properties of epitaxial magnetite (Fe3O4) thin films having a varying density of antiphase boundaries (APBs) were investigated as a function of temperature and frequency. Temperature dependence of noise exhibits a similar behavior to that of resistivity for all the films. The magnitude of normalized noise (Sv/V2) decreases with the increasing film thickness, which correlates well with the density of APBs. The quantitative feature of noise, i.e., Hooge parameter has a strong thickness dependence at low temperatures which implies that the APBs play an important role in determining the transport mechanism in epitaxial Fe3O4 films.
http://hdl.handle.net/2262/40394
Marked
Mark
Spin-polarized electron tunneling across magnetic dielectric
(2005)
SHVETS, IGOR
Spin-polarized electron tunneling across magnetic dielectric
(2005)
SHVETS, IGOR
Abstract:
This letter deals with a magnetic tunnel junction having spin filtering by a magnetic barrier. We performed experiments in which a relatively strong external field rotates magnetizations of both ferromagnetic electrodes in the tunnel junction with the magnetic barrier simultaneously so that the two are always parallel to each other. The tunnel magnetoresistance induced in this way was over 16% at 300 K. The angular dependency of the tunnel current on the layer magnetizations indicates that the barrier contains antiferromagnetic oxide. To achieve the described effect the magnetic electrode of the junction was oxidized prior to forming the Al2O3 layer.
http://hdl.handle.net/2262/40397
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Mark
Study of magnetoresistance of epitaxial magnetite films grown on vicinal MgO (100) substrate
(2005)
SHVETS, IGOR; ARORA, SUNIL KUMAR
Study of magnetoresistance of epitaxial magnetite films grown on vicinal MgO (100) substrate
(2005)
SHVETS, IGOR; ARORA, SUNIL KUMAR
Abstract:
The magnetoresistance sMRd studies of magnetite thin films deposited on vicinal MgO substrates show an enhanced MR along the miscut direction as compared to the direction perpendicular to it. The MR anisotropy increases with the decrease in temperature and peaks at the Verwey transition. The increase in magnetoresistance and anisotropy behavior is attributed to the formation of a greater number of out-of-plane shifted antiphase boundaries due to the step edges on vicinal MgO substrates. These local electronic and spin structure modifications at the APBs introduce additional spin scattering and are responsible for the increase in MR along the miscut
http://hdl.handle.net/2262/40398
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Mark
Degradation and breakdown characteristics of thin MgO dielectric layers
(2010)
O'Connor, Robert; Hughes, Greg; Casey, Patrick; Newcomb, Simon B.
Degradation and breakdown characteristics of thin MgO dielectric layers
(2010)
O'Connor, Robert; Hughes, Greg; Casey, Patrick; Newcomb, Simon B.
Abstract:
MgO has been suggested as a possible high-k dielectric for future complementary metal-oxide semiconductor processes. In this work, the time dependent dielectric breakdown (TDDB) characteristics of 20 nm MgO films are discussed. Stress induced leakage current measurements indicate that the low measured Weibull slopes of the TDDB distributions for both n-type and p-type devices cannot be attributed to a lower trap generation rate than for SiO2. This suggests that much fewer defects are required to trigger breakdown in MgO under voltage stress than is the case for SiO2 or other metal-oxide dielectrics. This in turn explains the progressive nature of the breakdown in these films which is observed both in this work and elsewhere. The reason fewer defects are required is attributed to the morphology of the films.
http://doras.dcu.ie/15579/
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Photoemission study of the SiO₂conversion mechanism to magnesium silicate
(2010)
Casey, Patrick; Hughes, Greg
Photoemission study of the SiO₂conversion mechanism to magnesium silicate
(2010)
Casey, Patrick; Hughes, Greg
Abstract:
The objective of this work is to investigate interface chemistries which minimize the interfacial silicon oxide transition region at Si/high-k dielectric interfaces. We report on the mechanism by which a silicon native oxide layer is converted into magnesium silicate. The deposition of metal Mg onto a SiO native oxide surface resulted in the formation of a magnesium silicide in addition to substochiometric silicon oxides and a significant decrease in the oxidised silicon signal. Annealing to 300 °C resulted in the decomposition of the magnesium silicide, oxidation of the Mg, and the desorption of excess metallic Mg. Subsequent annealing to 500 °C resulted in converting the SiO2 into magnesium silicate. The results suggest that the decomposition of the Mg silicide in the presence of the residual native oxide facilitates silicate formation at 500 °C. Due to the reported thermal stability of Mg silicate it is suggested that this process may be beneficial in modifying the interface char...
http://doras.dcu.ie/15580/
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Mark
High resolution photoemission study of SiOx/Si(111) interface disruption following in situ HfO₂deposition
(2009)
McDonnell, Stephen; Brennan, Barry; Hughes, Greg
High resolution photoemission study of SiOx/Si(111) interface disruption following in situ HfO₂deposition
(2009)
McDonnell, Stephen; Brennan, Barry; Hughes, Greg
Abstract:
We report on an in situ high resolution core level photoemission study of the early stages of interface formation between an ultrathin SiOx layer ( ∼ 0.3 nm) grown on the atomically clean Si(111) surface and a HfO2 dielectric layer. Si 2p core level spectra acquired at 130 eV photon energy reveal evidence of a chemically shifted component on the lower binding energy side of the substrate peak which is attributed to interface defect states resulting from the incorporation of silicon atoms from the substrate into the interfacial oxide at room temperature. This evidence of Si/SiOx interface disruption would be expected to increase charge carrier scattering mechanisms in the silicon and contribute to the generally observed mobility degradation in high-k stacks with ultrathin silicon oxide interface layers.
http://doras.dcu.ie/15581/
Marked
Mark
Atomic resolved material displacement on graphite surfaces by scanning tunnelling microscopy
(1992)
Moriarty, Philip; Hughes, Greg
Atomic resolved material displacement on graphite surfaces by scanning tunnelling microscopy
(1992)
Moriarty, Philip; Hughes, Greg
Abstract:
Atomic scale modifications and subsequent atomic resolution imaging has been achieved on the highly oriented pyrolytic graphite surface in air. Application of short pulse voltages, above a minimum threshold voltage of 3.5 V, across the tunneling gap results in the displacement of a layer or more of atoms to form a hole and create a neighboring mound or ‘‘nanodot’’ from the displaced atoms. We have found a correlation between the hole and ‘‘nanodot’’ volume at the atomic level and observe an asymmetric displacement of material in all cases of feature creation. Nanofeatures as small as four carbon atoms at beta sites have been created. Our experimental observations are consistent with the modification process depending on the gradient in the electric field induced by the rise time of the bias pulse voltage and not the pulse duration. Interesting faceting behavior has also been observed around some hole edges. Tip bias pulsing sometimes induced a tip, and not a surface modification, re...
http://doras.dcu.ie/15582/
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